Conventionally, there exists a battery apparatus that is obtained by connecting in parallel a plurality of storage batteries, each of which includes a plurality of electric storage elements connected in serial to have the high voltage, so as to realize increase in capacity. In a case where the plurality of storage batteries is connected in parallel, when electric-storage states of the storage batteries are different from each other, there exists in this electric storage apparatus a risk that a rush current flows from a storage battery having a high electric potential to a storage battery having a low electric potential, thereby leading to breakage.
Thus, there exists an electric storage apparatus that is provided in a hybrid automobile, for example, and connects in parallel a plurality of storage batteries through resistances when an ignition switch is turned OFF so as to equalize the electric potentials of the storage batteries while easing a rush current (see Japanese Laid-open Patent Publication No. 2013-240142, for example).
However, in the conventional electric storage apparatus, there exists in some cases a case where a part of the electric storage elements are over-charged or over-discharged when the plurality of the storage batteries is connected in parallel.